1. Field of the Invention
The invention concerns a circular saw having an improved tooth geometry which is especially adapted for cutting hard, brittle metals.
2. Description of the Prior Art
Circular saw teeth with carbide inserts, initially having a cylindrical or spherical shape are known to those of ordinary skill in the art. For example, Goehle U.S. Pat. No. 2,675,603 discloses the use of a cylindrical carbide element as a tooth in the context of a composite circular saw. While the insert is cylindrical in shape, it is eventually ground and faced so as to have a conventional working surface. Kolesch U.S. Pat. No. 3,537,491 and Tyler U.S. Pat. No. 3,788,182 both disclose the use of spherical carbide ball inserts adapted for use in other circular saws. However, as in the case of Goehle, the spheres are subsequently faced and the remaining rounded section of the sphere is not in actuality the working surface. Lewis U.S. Pat. No. 485,503, Bruestle et al, U.S. Pat. No. 2,860,863 and LaVelle, U.S. Pat. No. 3,380,497 all disclose prior art circular saws having a rounded profile when seen from either the front or back of the tooth. Again, the working surface is neither cylindrical, conical or spherical. Osgood, U.S. Pat. No. 238,521 and Pioche, U.S. Pat. No. 1,334,633 likewise disclose saws in which the side view profile of the tooth is rounded or cylindrical in some aspects but wherein the working surface is neither spherical, conical or cylindrical.
The problem encountered with old-fashioned carbide tooth saws is two-fold. One of the problems associated with carbide tips is that the carbide insert is hard and brittle and cannot take interrupted cutting. During interrupted cutting the shock loading on the teeth is so great that the teeth will frequently break. The second problem associated with conventional carbide insert saws is that carbide has an affinity for many metals that it cuts. Frequently, a metal chip will get stuck on the face of the carbide insert or in the gullet thereunder. According to prior art methods of cutting, it was often necessary to get rid of this excess metal by means of an air blast or brushes. Unfortunately, these techniques were not always satisfactory and resulted in great blade deterioration.
Recently, a saw blade having an improved metal cutting geometry was disclosed in U.S. Pat. Nos. 3,576,061 and 3,619,880. This is often referred to as the "German" geometry. According to those inventions, an improved cutting characteristic could be achieved by slightly beveling the top face of the tooth down towards the side of the tooth. This technique is similar to the technique of "breaking the corners" in order to prolong saw blade life. While the saws disclosed in U.S. Pat. Nos. 3,576,061 and 3,619,880 do display some improved cutting characteristics, they are nevertheless difficult to manufacture because they require several different grinding steps in order to achieve a satisfactory geometry. What was desired in this context was a saw blade that exhibited cutting characteristics better than those disclosed in U.S. Pat. Nos. 3,576,061 and 3,619,880 and which were easier to grind and regrind. It was in the context of the foregoing prior art and prior art problems that the following invention arose.